Analytical potentials for HF dimer and larger HF clusters from ab initio calculations

A new ab initio potential for hydrogen fluoride dimer is presented, constructed from properties calculated for the monomer and intermolecular perturbation theory calculations on the dimer. The potential is split into clearly defined contributions. The long-range electrostatic energy is represented by a distributed multipole model with multipoles up to hexadecapole. The induction energy is modelled by means of polarizabilities up to rank 2 at the center of mass. The repulsion energy is described by an anisotropic exponential site-site model. For the dispersion, two models have been used: a one-site anisotropic and a two-site isotropic model, both incorporating damping functions. The geometries, binding energies, and barrier height to tunneling motion are in good agreement with previous calculations. We also compare the classical and quantum corrected second virial coefficient with the limited data available. The potential is extended to larger clusters, the induction energy accounting for many-body contributions to the energy. For the trimer to the hexamer, we have characterized minima and transition states and decomposed the total interaction energy into its n-body components.